Composition for use in electromagnetic wave shielding

ABSTRACT

A shielding composition has an electromagnetic wave shielding property and also an injection molding property. The composition comprises at least one kind of embedding material selected from a group consisting of plasticized vinyl chloride and acrylonitrile-butadiene-styrene resin, and copper or copper alloy fiber having a diameter of 1-100 μm and a length of 0.5-10 mm embedded in said embedding material. The amount of the fibers is 30-70% by weight of the total composition.

FIELD OF THE ART

This invention relates to a composition for use in electromagnetic waveshielding suitable for electronic apparatuses, and electronic parts,etc. and having an excellent in injection moldability.

BACKGROUND OF THE ART

In order to industrially manufacture at low cost an interface bus cablefor connecting electronic components such as peripheral units forpersonal computers while avoiding an electric wave leaking, it isnecessary to insulate the connection between cores and terminals of thebus cable and to cover the thus insulated connection with anelectromagnetic shielding material by injection molding. However,shielding material heretofore proposed does not have a sufficientfluidity above the melting point or softening point of a base polymer.Hence, there was a problem in that it was difficult to properly placethe shielding material by injection molding techniques so that theshielding material would assume the shape defined by a metal mold or inthat the molded material would not have a smooth surface. It wasimpossible to obtain properly shaped shielding members having a smoothsurface.

DISCLOSURE OF THE INVENTION

In view of the problems described above, this invention proposes a novelcomposition for use as electromagnetic wave shielding having both anexcellent electromagnetic wave shielding ability and an injectionmoldability. The composition proposed according to the inventioncomprises at least one kind of a suspension or embedding agent selectedfrom a group consisting of plasticized vinyl chloride resin, andacrylonitrile-butadiene-styrene resins and fibers suspended or embeddedin said agent, said fibers consisting of copper or of a copper alloy andhaving a diameter of 1-100 μm and a length of 0.5-10 mm. The fibercontent contained in the composition amounts to 30-70% by weight of thecomposition.

The plasticized vinyl chloride resin used by the invention may be, forexample a vinyl chloride homopolymer, a vinyl chloride copolymer, or aninternally plasticized vinyl chloride copolymer, etc, plasticized by theuse of a plasticizer or an organic high polymer compatible with vinylchloride resin. A composition is particularly useful for the presentpurposes if it has a vicosity, at a temperature of 180° C., measured bya Brabender plastograph, in the range of 50-3,000 m-g, more particularly100-2,000 m-g. The unit: m-g is used in the present disclosure for allviscosity values as measured by said plastograph at said temperaturecondition. more particularly 100-2,000 m-g is suitably used. Such acomposition shows an excellent injection moldability in a state in whichmetal fibers to be described below, are compounded in large quantities.

The above-mentioned vinyl chloride homopolymer may be produced by aconventional known polymerization process such as an ordinary suspensionpolymerization, an emulsion polymerization, a bulk polymerization or asolution polymerization. A homopolymer is particularly suitable for thepresent purpose if its mean degree of polymerization (P) is within therange of 300-2,000, especially 400-1,100, because it has desirableinjection molding features.

The above-mentioned vinyl chloride copolymer may be produced by an abovementioned conventional process, and has the characteristic in that (a)the vinyl chloride content is at least 50% by weight and particularly atleast 80% by weight, (b) the viscosity is lower than that of vinylchloride homopolymer, and (c) the mean degree of polymerization iswithin the range of 300-2,000 and especially 400-1,100. Such vinylchloride copolymer includes (1) copolymers of vinyl chloride with atleast one kind of monomer capable of effecting radical polymerizationwith vinyl chloride, for example, olefin, diene, unsaturated carboxylicacid and its esteric derivatives, unsaturated nitryl, aromatic vinyl andit derivatives; (2) graft polymers obtained by grafting upon vinylchloride homopolymer or the above vinyl chloride copolymer at least onekind of monomer capable of effecting radical polymerization with theabove vinyl chloride; (3) copolymers of vinyl chloride and polymercopolymerizable with vinyl chloride, for example, olefin-vinyl estercopolymer such as ethylene-vinyl acetate copolymer, olefin-alkylacrylatecopolymer such as ethylene-methylacrylate, olefin-alkyl methacrylatecopolymer such as ehtylene methyl methacrylate, polyolefin type polymersuch as polyethylene, ethylene-propylene copolymer, ethylene-propylenecopolymer, chlorinated polyethylene and chloro-sulfonated polyethylene,polyether type polymer such as ethylene epichlorohydrine copolymer,diene type elastomer such as polybutadiene and polyisoprene,acrylonitrile-butadiene-styrene copolymer, methylmethacrylate-butadiene-styrene copolymer, etc.; (4) copolymers of vinylchloride and at least one kind of the above polymers copolymerizablewith vinyl chloride and at least one kind of above monomers capable ofeffecting radical polymerization with vinyl chloride.

Particularly, a copolymer of vinyl chloride and a monomer capable ofeffecting radical polymerization with vinyl chloride, is desirable, andin addition, the copolymer which is 80-99.5% by weight of the vinylchloride content, is particularly desirable.

As a plasticizer there may be used a conventional plasticizer for vinylchloride resin, for example, (1) esters phthalate such as di2-ethylhexyl phthalate, di n-octyl phthalate, diisodecyl phthalate,diisonyl phthalate and mixed basic ester phthalate having 7-11 carbons;(2) esters phosphate such as tricresyl phosphate, triphenyl phosphate,trioctyl phosphate, cresyldiphenyl phosphate; (3) aromatic carboxylicacid esters, such as ester trimelliticate such as octyl trimelliticate,ester trimesicate, ester pyromelliate; (4) aliphatic dibasic esters suchas diethyl adipicate, diisodecyl adipicate, dioctyl sebacicate; (5)polyesters of adpinic acid or sebacic acid; and (6) chlorinatedparaffins.

The amount of the plasticizer described above for plasticizing vinylchloride resin to have the viscosity mentioned above can easily bedetermined by an experiment, but generally, the amount of use of thisplasticizer is 10-80 parts per 1,000 parts by weight of vinyl chlorideresin.

As an organic high polymer compatible with vinyl chloride resin andbeing able to plasticize the vinyl chrolide resin, there may be used,for example, acrylonitrile-butadiene rubber, thermoplastic urethane,thermoplastic polyester, ethylene-vinyl acetate copolymer containing ahigh proportion of vinyl acetate, say, more than 35% by weight, and thelike. The mentioned organic high polymers may be mixed with vinylchloride resin alone or in combination with one of the plasticizersmentioned above.

Of the vinyl chloride copolymers mentioned above, those which are withinthe above range may be used alone as internally plasticized vinylchloride resins.

The various plasticized polyvinyl chloride resins of the type describedabove which are used by the invention may be used alone or in mixture ofmore than two kinds. In addition, one or more than two kinds of ordinarychemical agents may be compounded such as a stabilizer, lubricant,pigment, flame retarder, if necessary, which are usually compounded withvinyl chloride resin. However, it is to be noted that the amount of thechemical agent should be such that the viscosity of vinyl chloride resinobtained by the compounding should be limited within the range describedabove.

A stabilizer which is usually used for molding vinyl chloride resins,may also be used for the present purposes, for example (1) a lead typestabilizers such as dibasic lead sulfate, dibasic lead phosphonate,dibasic lead stearate; (2) tin type stabilizers such as dibutyl tinlaurate, dibutyl tin maleate, dibutyl tin fumarate; (3) complexstabilizers such as Ba.Zn complex stabilizer, Ba.Ca complex stabilizer,and so on, may be used.

A conventional flame retarder used in vinyl chloride resin, for example,antimony trioxide, alumina hydrate, etc, may be used for the presentpurpose.

In the invention, an acrylonitrile-butadiene-styrene copolymer may beused in the form of a base polymer manufactured by a polymer blendingprocess such as a kneading-mixing process, a latex mixing process or agraft polymerization process such as emulsion polymerization, bulkpolymerization, suspension polymerization, or the like process. Ifnecessary, ordinary chemical agents such as a pigment and an oxidationretarder in usual amounts may be compounded into theacrylonitrile-butadiene-styrene copolymer.

The copper or copper alloy used in the invention is pure copper or acopper alloy such as an alloy of copper with at least one kind ofelements such as zinc, tin, lead, phosphor, iron, manganese, aluminum,nickel, silicium, beryllium, silver, tellurium, cadmium, chromium,selenium, zirconium. The alloy has a copper content of at least 50% byweight, for example, and employing electrolytic copper, deoxidizedcopper, oxygen free copper, free cutting copper, red copper, brass,bronze, Corson alloy, Heussler alloy, German silver, cupro-nickel,beryllium copper, silver copper, chromium copper, and the like.

Fibers made of the above-mentioned copper or copper alloy having adiameter of 1-100 μm and a length of 0.5-10 mm, are superior in softnessor pliability to other metal fibers and are also superior in theirkneading and mixing properties with respect to vinyl chloride resin andacrylonitrile-butadiene-styrene resin, so that the copper or the copperalloys mentioned above are both essential and excellent for theproduction of a composition of the invention which has excellentinjection moldability qualities and electroconductivity qualities.

Fibers of copper alloys consisting essentially of copper and zinc in thefollowing weight ratio range of copper to zinc, namely 95:5-60:40,particularly 80:20-63:35, are especially desirable because of theirsoftness or pliability and because of their injection moldablity.

The composition of the invention comprises plasticized vinyl chlorideresin (for example, consisting of vinyl chloride resin and aplasticizer) and/or acrylonitrile-butadiene-styrene copolymer, copper orcopper alloy fiber, and other chemicals compounded, if necessary, andthe quantity of the copper or copper alloy fiber contained in thecomposition of the invention is 30-70% by weight.

When the copper or copper alloy fibers are shorter in length than 0.5 mmor smaller in the amount of use than 30% by weight, the conductioneffect is reduced and, on the other hand, when the fibers used arelarger in length than 10 mm or larger in diameter than 100 μm, aninjection molder is clogged up, or when it is larger in the amount ofuse than 70% by weight, the viscosity of the composition increasesextremely, enough so as to decrease the injection moldability in anyevent. Also, when the fibers used are finer in diameter than 1 82 m, thefibers are cut and reduced in length at the time of mixing with theplasticized vinyl chloride resin, with the result that the compositionhas a reduced conductivity.

When the composition of the invention has a volume resistivity withinthe range of 0.005-0.5 Ωcm, particularly 0.005-0.1 Ωcm, it has a goodsurface conductivity and especially it produces an electromagnetic waveshielding effect. On the other hand, when the viscosity of thecomposition of the invention is 100-5,000 m-g, particularly 200-2,000m-g, it has an especially excellent injection moldability. It ispossible to produce the composition of the invention having the aboveproperties by controlling the size of the fibers used and thequantities. Desirable copper or copper alloy fibers have a diameter of20-80 μm and particularly 40-60 μm, and a length of 1-6 mm, particularly2-4 mm. Also, the quantity of fibers is preferably 35-65% by weight andparticularly 40-60% by weight.

The composition of the invention may be produced with the aid of ageneral mixer such as a two-roller mixer, a Banbury mixer (trade name)in such various ways of addition that a plasticizer, copper or copperalloy fiber and other chemicals are together added to the vinyl chlorideresin or that vinyl chloride resin is beforehand plasticized by aplasticizer and then the remaining chemical components are added to theplasticized vinyl chloride resin.

The composition of the invention has excellent electromagnetic waveshielding and injection molding properties. Hence, the presentcomposition is suitable for use in covering, by injection molding, theleaking wave generating portion of various electronic devices andelectronic components which cause radio wave interference. Particularly,when the composition of the invention is used as a shielding material ofa connector for a bus cable forming an interface for personal computercomponents, which in recent years have been used in steadily increasingnumbers in homes, the present composition provides a great improvementin the prevention of wave interferences caused by electromagnetic waveleaks as compared to conventional connectors used for example, in radioreceivers and television sets.

PREFERRED EMBODIMENTS OF THE INVENTION

A detailed description will now be given of examples according to theinvention and of contrast examples the latter being comparable examples.Symbols for the compositions used in the invention examples and contrastexamples, and contents of the compositions are shown in Table 1 in whichthe part and percentages used are represented by parts by weight andpercent by weight figures, respectively.

Table 2 shows compositions and properties of the invention examples(Example Nos. 1-23) and contrast examples (Contrast Example Nos. 1-10).Furthermore, the compounding ratio shown in the base polymer compositionin the Table represents parts by weight, and the percentage of metalfiber represents percent by weight figures of the fiber contained in thecomposition of the invention and contrast examples. All theconstituents, except the metal fiber, of the composition in each exampleare sufficiently mixed by two rollers which were beforehand heated to atemperature of 180° C., and then the metal fiber was added to the thussufficiently mixed composition on the two rollers and the mixing wasthen continued to obtain an intended composition.

The characteristics of the invention and of the reference examples weredetermined and rated by the following processes.

INJECTION MOLDABILITY

For rating the injection moldability of the present invention a buscable for an interface in personal computers was prepared. The bus cablewas constructed by placing a layer of shielding braid on a bundle of 24cores, a connector having 25 contacts was mounted to each end of themulticore cable having an outer diameter of 1.5 mm, a protective sheathconsisting of vinyl chloride homopolymer containing a plasticizer wasapplied to the cable, the conductor of each core was directly connectedto its respective contact, and the copper shielding braid was connectedthrough a drainage wire to one remaining contact.

The surface of the above connection portions was insulated. In thisstate, the cable of the invention and of the contrast examples wereinjection-molded on the surface of the connector at both ends of the buscable placed in the mold having a controlled temperature of 50° C.-70°C. and on the surface of a part of the cable away from the connector, bythe use of a 2.5 oz. injection molder having a nozzle diameter of 2.5mm, a barrel temperature of 180° C., and operating with an extrusionpressure of 50 kg/cm². The results of the examples are shown in fivesteps as follows.

Grade A (excellent) . . . . There is no dimensionally broken portion andgloss and smoothness on the surface are also good.

Grade B (good) . . . . There is no dimensionally broken portion and thesurface is smooth but slightly lacking in gloss.

Grade C (rather good) . . . . There is no dimensionally broken portionbut there are partially coarse portions on the surface.

Grade D (passable) . . . . There is no dimensionally broken portion inthe portion near the terminal end portions of resin flow path inside themetal mold and in the bellows portion at the joint of the cable. Inaddition, most of the surface is rough.

Grade E (no good) . . . . The nozzle is stopped up, or a too highviscosity makes the injection molding impossible.

VOLUME RESISTIVITY

The composition was subjected to pressure forming under the conditionsof a temperature of 180° C., a pressure of 100 kg/cm² and a duration of5 min. as determined by a process specified in ASTM D-991-68 per sheetof 1 mm in diameter and 10 cm both in length and in width.

ELECTROMAGNETIC WAVE SHIELDING PROPERTY

The shielding effect was determined for each bus cable obtained byrating the injection moldability by the absorption clamp process inaccordance with IEC CISPR Pub. 16. Incidentally, a bus cable before ashielding material was injection-molded over the cable was used as acontrol (see Table 2) or reference cable.

                                      TABLE 1                                     __________________________________________________________________________    Abbreviations    Contents                                                     __________________________________________________________________________    Organic High Polymer Constituting                                             a Base of Composition                                                         PVC1             Vinyl chloride homopolymer (.sup.--P: 1500)                  PVC2             Vinyl chloride homopolymer (.sup.--P: 800)                   PVC3             Vinyl chloride homopolymer (.sup.--P: 600)                   VCVA1            Vinyl chloride-vinyl acetate copolymer (.sup.--P: 1100,                       VC: 98%)                                                     VCVA2            Vinyl chloride-vinyl acetate copolymer (.sup.--P: 800,                        VC: 98%)                                                     VCE1             Vinyl chloride-ethylene copolymer (.sup.--P: 1100, VC:                        98%)                                                         VCE2             Vinyl chloride-ethylene copolymer (.sup.--P: 600, VC:                         97%)                                                         VCE3             Vinyl chloride-ethylene copolymer (.sup.--P: 1100, VC:                        93%)                                                         VCU              Vinyl chloride-urethane copolymer (.sup.--P: 1100, VD:                        50%)                                                         EVAVC            Ethylene-vinyl acetate-vinyl chloride graft copolymer                         (.sup.--P: 1100, VC: 50%, VA: 25%, E: 25%)                   ABS              Acrylonitrile-butadiene-styrene copolymer                    PE               Polyethylene (d: 0.925, MI: 1)                               Plasticizer or High Organic                                                   Polymer for Use in Plasticization                                             DOP              Di n-octyl phthalate                                         DIDP             Diisodecyl phthalate                                         TOTM             Trioctyl trimelliticate                                      DINP             Diisononyl phthalate                                         TCP              Tricresyl phosphate                                          TOP              Trioctyl phosphate                                           TPP              Triphenyl phosphate                                          NBR              Acrylonitrile-butadiene rubber                               Metal Fiber                                                                   Brass 1          7/3 brass (diameter: 30 μm, length: 6 mm)                 Brass 2          7/3 brass (diameter: 50 μm, length: 4 mm)                 Brass 3          7/3 brass (diameter: 60 μm, length: 2 mm)                 Brass 4          6/4 brass (diameter: 50 μm, length: 4 mm)                 Brass 5          6/4 brass (diameter: 60 μm, length: 2 mm)                 Brass 6          Naval brass (diameter: 50 μm, length: 3 mm)               Brass 7          7/3 brass (diameter: 0.5 μm, length: 5 mm)                Brass 8          7/3 brass (diameter: 200 μm, length 3 mm)                 Brass 9          7/3 brass (diameter: 10 μm, length: 0.1 mm)               Brass 10         7/3 brass (diameter: 50 μm, length: 30 mm)                Red copper 1     9/1 red copper (diameter: 50 μm, length: 3 mm)            Red copper 2     9/1 red copper (diameter: 60 μm, length: 1 mm)            Pure copper 1    Electrolytic copper (diameter: 20 μm, length: 6 mm)       Pure copper 2    Electrolytic copper (diameter: 60 μm, length: 2 mm)       Al               Pure aluminum (diameter: 50 μm, length: 3 mm)             Ni               Pure nickel (diameter: 50 μm, length: 3 mm)               Other Chemicals                                                               Sb.sub.2 O.sub.3 Antimony trioxide                                            AO               Alumina hydrate, Al.sub.2 O.sub.3.3H.sub.2 O                 TS               Tribasic lead sulfate                                        LFOS             Dibasic lead phosphonate                                     ABT              Ba--Zn dibutyl tin laurate                                   Ba.Zn            Ba--Zn compound stabilizer (produced by Nippon Ink K.K.                       under the trade name "INSTAS TARB M 7268 T")                 SA               Stearic acid                                                 __________________________________________________________________________     Note:                                                                         The symbol .sup.--P represents mean degree of polymerization; VC content      of vinyl chloride constituent; VA content of vinyl acetate constituent; E     content of ethylene constituent; d density; and MI represents a melt          index.                                                                   

    TABLE 2       Contrast Contrast Contrast Contrast Contrast Contrast Contrast     Contrast Contrast Contrast  Control Example 1 Example 2 Example 3     Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 Example 10     Example 1       Composition                  Base -- PE 100 PVC 1 100  same as VCVA     100  same as same as VCVA1 100  same as same as same as VCVA1 100     Composition    DOP 50  left DIDP 50  left left DZDP 50  left left left     DOP 50  (part by wt.)    TS 5  DBL 5   DBL 5    TS 5     SA 1  SA 1   TS     3    SA 3 Metal Fiber -- Brass 1 Al Ni Brass 1 Brass 1 Al brass 7  brass     8 brass 9 brass 10 brass 1 (% by weight)  50 50 50 20  80 80 50 50 50 50      40 Characteristics Injection -- good not good good excellent good not     good excellent not good excellent not good excellent Moldability Volume     -- 6 × 10.sup.-1 4 × 10.sup.-1 3.5 × 10.sup.-1 2     × 10.sup.2 8 × 10.sup.-2 9 × 10.sup.-2 1 ×     10.sup.1 3 × 10.sup.-2 1.5 × 10.sup.1 4 × 10.sup.-2 9     × 10.sup.-2 Resistivity Ω cm Electromagnetic Wave Shielding     Effect (dB)  30 MHz 10 50 -- 56 23  70 -- 12 -- 13 --  70  100 MHz 10 50     -- 56 18 >70 -- 14 -- 12 -- >70  300 MHz 10 50 -- 60 13 >70 -- 13 -- 15     -- >70  500 MHz 15 55 -- 60 17 >70 --  18 -- 16 -- >70 1000 MHz 20 60 --     70 20 >70 -- 15 -- 16 -- >70 Viscosity (m - g) -- 5400  6200  5350  1300      5450 7100  1400  1700  1450  1750       1400                                   Example 2 Example 3 Example 4     Example 5 Example 6 Example 7 Example 8 Example 9 Example 10 Example 11     Example 12 Example 13       Composition                    Base VCV1 100  same as same as same as     same as same as VCVA1 100  PVC1 100  PVC2 100  PVC3 100  VCVA1 100  VCE1     100  Composition DOP50  left left left left left DOP 50  NBR 20 TOTM 40     TOTM 40 DINP 45 DINP 45 (part by wt.) TS 5      TS 5 DIDP 50 DBT  8 DBT     7 TS  7 LFOS  7  SA 3      SA 3 LFOS  5 Metal Fiber brass 1 brass 1     brass 2 brass 3 brass 4 brass 5 brass 6 red pure pure red brass 3 (% by     weight)  50  60  48  48  48  48  48 copper 1 copper 1 copper 2 copper 2     50          50  50  50  50 Characteristics Injection excellent excellent     excellent excellent excellent excellent excellent excellent good good     excellent excellent Moldability Volume 6 × 10.sup.-2 1 ×     10.sup.-2 2.5 × 10.sup.-2 5.5 × 10.sup.-2 3 ×      10.sup.-2 4.4 × 10.sup.-2 3.8 × 10.sup.-2 8 ×     10.sup.-2 4.3 × 10.sup.-2 3 × 10.sup.-2 2 × 10.sup.- 2     4 × 10.sup.-2 Resistivity Ω      cm Electromagnetic Wave Shielding Effect (dB)   30 MHz >70 >70 >70 >70     >70 >70 >70 >70 >70 >70 >70 >70  100 MHz >70 >70 >70 >70 >70 >70 >70 >70     >70 >70 >70 >70  300 MHz >70 >70 >70 >70 >70 >70 >70 >70 >70 >70 >70 >70      500 MHz >70 >70 >70 >70 >70 >70 >70 >70 >70 >70 >70 >70 1000 MHz >70     >70 >70 >70 >70 >70 >70 >70 >70 >70 >70 >70 Viscosity (m - g) 1500 1650     1480 1440 1500 1550 1480 1250  850      650 1700 1450                          Example 14 Example 15 Example 16 E     xample 17 Example 18 Example 19 Example 20 Example 21 Example 22 Example     23       Composition                    Base VCE2 100  VCE3 100  VCU 100  EVAVC     100  ABS 100 same as same as VCVA2 100  VCE2 100  VCE2 100  Composition     TCP 40 TOP 40 TPP 10 DOP 10   left left TCP 40 TCP 40 TCP 50 (part by     wt.) Ba.Zn  5 TS  7 TS  7 TS  8     TS 10 TS 10 LFOS 10     Sb.sub.2 O.sub.3 10 Sb.sub.2 O.sub.3 10 AO 10 Metal Fiber brass 3 brass     3 brass 2 brass 4 brass 1 brass 2 pure brass 3 brass 3 same as (% by     weight)  50  50  50  50  55  45 copper 1  45  45 left         45     Characteristic Injection good good excellent excellent excellent     excellent excellent good good good Moldability Volume 3 ×      10.sup.-2 2.5 ×  10.sup.-2 1 × 10.sup.-2 1 ×      10.sup.-1 1.2 × 10.sup.-2 6 × 10.sup.-2 3 × 10.sup.-2     3.8 × 10.sup.-2 5.2 × 10.sup.-2 5.3 × 10.sup.-2     Resistivity Ω cm Electromagnetic Wave Shielding Effect (dB)  30     MHz >70 >70 >70 >70 >70 >70 >70 >70 >70 >70  100 MHz >70 >70 >70 >70 >70     >70 >70 >70 >70 >70  300 MHz >70 >70 >70 >70 >70 >70 >70 >70 >70 >70     500 MHz >70 >70 >70 >70 >70 >70 >70 >70 >70 >70 1000 MHz >70 >70 >70 >70     >70 >70 >70 >70 >70 >70 Viscosity (m - g)  800  600  900 1700  800  750     740  660  720      820

What is claimed is:
 1. An electromagnetic wave shielding compositionsuitable for press forming or injection molding purposes, comprising anembedding material selected from a group consisting of plasticized vinylchloride resin and acrylonitrile-butadiene-styrene resin, and copper orcopper alloy fibers embedded in said embedding material, said fibershaving a diameter of 1-100 μm and a length of 0.5-10 mm, wherein theamount of the fibers is 30-70% by weight of said composition, saidcomposition having a shielding effect of at least 70 (dB) in a frequencyrange of about 30 MHz to about 1000 MHz and a volume resistivity in therange of about 0.005 to about 0.5 Ωcm.
 2. The composition according toclaim 1, having a viscosity in the range of 200-2,000 m-g at atemperature of 180° C.
 3. The composition according to claim 1, whereinsaid plasticized vinyl chloride comprises of vinyl chloride copolymerand a plasticizer, said vinyl chloride copolymer being at least 50% byweight in vinyl chloride content and wherein said vinyl chloridecopolyer has a mean degree of polymerization within the range of 400 to1,200.
 4. The composition according to claim 3, wherein said vinylchloride copolymer is a copolymer of vinyl chloride and at least onekind of monomers, said monomers being capable of effecting radicalpolymerization with vinyl chloride, wherein said vinyl chloride is80-99.5% by weight in content.
 5. The composition according to claim 1,wherein said copper or copper in said copper alloy is pure copper. 6.The composition according to claim 1, wherein said copper alloy consistsessentially of copper and zinc, and wherein the copper ranges from60:95% by weight of the copper alloy and the zinc ranges from 40:5% byweight of the copper alloy.
 7. A method of shielding anelectromagnetically radiating device against radiation leaks, comprisingthe following steps:(a) preparing, by mixing, an electromagnetic waveshielding composition comprising an embedding material selected from agroup consisting of plasticized vinyl chloride resin andacrylontrile-butadiene-styrene resin, and copper or copper alloy fibersembedded in said embedding material, said fibers having a diameter of1-100 μm and a length of 0.5-10 mm, wherein the amount of the fiber is30-70% by weight of said composition, and (b) injection molding the soprepared composition onto said radiating device for preventing saidradiation leaks, said composition having a shielding effect of at least70 (dB) in a frequency range of about 30 MHz to about 1000 MHz and avolume resistivity in the range of about 0.005 to about 0.5 Ωcm.